Free-Space Waveform Concealment via Aperiodic Symbol Timing
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Solution Overview
Problem
Current free-space communication techniques, despite encryption and obfuscation methods, still allow for signal interception and recovery of waveform metadata, such as symbol period and modulation type, by conventional receivers.
Innovation Solution
Aperiodically modulating the coherent waveform by adjusting symbol duration or inserting false symbols, which conceals the timing structure of the signal, making it impossible for conventional receivers to detect the signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional coherent or non-coherent receivers are used to intercept free-space transmissions, then the waveform metadata (such as symbol period and modulation type) can be detected and recovered, but the security and privacy of the transmitted data is compromised
Solution Approach 1:
The patent applies asymmetry by using different symbol durations for different symbols within the same data stream. This creates an asymmetric timing structure where the first symbol has a different duration than subsequent symbols, making it difficult for conventional receivers to detect waveform metadata while allowing the legitimate receiver (with knowledge of the asymmetric pattern) to properly decode the data
Solution Approach 2:
The patent changes the timing parameter (symbol duration) dynamically within the transmission. By varying the symbol duration between different symbols and using different durations for data symbols versus delimiter symbols, the system conceals waveform properties from interceptors while maintaining decodability for authorized receivers
2Reliability
If encryption techniques are used to protect transmitted data, then the data payload is encoded, but the transmitted waveform itself can still be intercepted and its properties analyzed
Solution Approach 1:
The patent segments the data stream into distinct symbols with different timing characteristics. By dividing the transmission into data symbols and delimiter symbols with different durations, and further segmenting data symbols into those with different durations, the system creates a segmented timing structure that obscures waveform properties while enabling structured decoding at the receiver
Solution Approach 2:
The patent incorporates delimiter symbols with distinct timing patterns as preliminary markers within the data stream. These delimiters with known timing characteristics serve as reference points that help the legitimate receiver synchronize and decode the asymmetric timing structure, while simultaneously confusing potential interceptors who lack knowledge of the delimiter placement and timing patterns
Data Source
AI summary
Aspects are generally directed to free-space transmitters, free-space receivers, and free-space communication methods. In one example, a free-space communication method includes acts of mapping a data payload to one or more symbols based on a symbol set defined by a digital modulation scheme, varying one or more properties of a signal waveform to phase modulate the signal waveform with the data payload, the one or more symbols each having a symbol duration that defines a timing structure of the modulated signal waveform, and fragmenting the timing structure of the modulated signal waveform to conceal one or more waveform properties of the modulated signal waveform.